Per cent. 



Manganese 0. 07 



Sulphm- . 00 



Barium . 04 



Cbroiniuni . 01 



Nickel .01 



Strontium .01 



Lithium . 01 



Chlorine .. 01 



Fluorine .01 



THE PROBLEM OF THE METALLIFEROUS VEINS, 189 



and may remark the rarity of the others; we may next set forth the 

 necessary percentages of each metal which make a deposit an ore; 

 that is, make it rich enough for profitable working. By comparison 

 we can grasp in a general way the amount of concentration which 

 must be accomplished by the geological agents in order to collect from 

 a naturally lean distribution in rocks enough of a given metal to pro- 

 duce a deposit of ore, and can then naturally pass to a brief discussion 

 and description of those agents and their operations. 



If the general composition of the crust of the earth is calculated as 

 closely as possible on the basis of known chemical analyses, the fol- 

 lowing table results. Avhich has been compiled by Dr. F. AV. Clarke, 

 of Washington, chief chemist of the IT. S. Geological Survey: " 



Per cent. 



Oxygen 47. 13 



Silicon 27. 89 



Aluminum 8. 13 



Iron 4. 71 



Calcium 3. 53 



Magnesium 2.04 



Potassium 2. 35 



Sodium 2. 08 



Titanium . 32 



Hydrogen . 17 



Carbon . 13 



Phosphorus . 09 



Elements less than 0.01 per cent are not considered abundant 

 enough to affect the total, and equally exact data regarding them are 

 not accessible. Among those given only the following appear which 

 are metals of importance as such in everj^day life : Aluminum 8.13, 

 iron 4.71, manganese 0.07, chromium 0.01, and nickel 0.01. They 

 rank, respectively, in the table, third, fourth, thirteenth, sixteenth, 

 and seventeenth. Of the five, iron is the only one of marked promi- 

 nence. No one of the remaining four is comparable in usefulness 

 with at least five other metals which are not mentioned, viz, copper, 

 lead, zinc, silver and gold. 



An endeavor has been made by at least one investigator. Prof. J. H. 

 L. Vogt, of Christiania, to establish some quantitative expression for 

 these other metals. His estimates are as follows : ^ 



Copper percentage beyond the fourth or fifth place of decimals — 

 that is, in the hundred thousandths or millionths of a per cent. 



Lead and zinc percentages in the fifth place of decimals, or in the 

 hundred thousandths of a per cent. 



Silver percentage two decimal places beyond copper, or in the 

 ten millionths to the hundred millionths of a per cent, or the ten 

 thousandths to the hundred thousandths of an ounce to the ton. 



o Bulletin 148, p. 13. 6 Zeitschrift fiir prak. Geologic, 1898, p. 324. 



Total 100.00 



